Fear of Rejection:

People have an innate longing to belong, to be accepted, to be acknowledged as being a part of someone or something.
So, it also happens that people do have fears or anxiety over the possibility that their quest to belong might be turned down, or that for some reason they might be cut-off from being friends with persons they cherish.

But really, what's this fear about? What feeds the fear?

Is it a silent inner belief or questioning that, maybe the person harbouring this fear is not good enough? Has not loved themselves enough? Have not come to terms with their level of competence?

When rejection happens, the person rejected often internalizes the event and often adopts percieved or self-created faults. Rejection brings people into touch with their insecurities, percieved or real. You start to become aware of all the ways that you are insufficient, all the ways you are not good enough etc. Whether these thoughts are real or not, it usually is a place where people don't want to be at. People would rather avoid the disappointment or hurt of being rejected. And if rejection has happened a few times before, for most people, rather than trying, only to eventually be rejected, they sometimes choose not to try again!